例句與造句

1. key strata is a rock seam which plays an important controlling roles in the movement of mining overlayer strata while the key strata is sometimes made up of two or more compound rock strata
   摘要在采場(chǎng)覆巖運(yùn)動(dòng)中起主要控制作用的巖層為關(guān)鍵層，而有時(shí)關(guān)鍵層是由2層或2層以上巖層形成的復(fù)合巖層所組成，我們稱其為復(fù)合關(guān)鍵層。
2. It's difficult to find overlayers in a sentence. 用overlayers造句挺難的